When a voltage is applied to an electrolyte membrane used in a fuel cell, hydrogen (H2) is converted into protons (H+), which move from one surface of the electrolyte membrane to the other surface thereof. When moving from one surface to the other surface through the electrolyte membrane, the protons are accompanied by a polar substance such as water, alcohol, or ammonia. The technique of compressing the gaseous polar substance using this phenomenon is called “electrochemical compression”. Compressors to which this electrochemical compression is applied are called “electrochemical compressors”. Patent Literatures 1 and 2 each describe a heat pump apparatus including an electrochemical compressor.